A computer is programmed to receive data concerning a current location of a vehicle, a plurality of gas prices at a plurality of gas stations, and a plurality of locations, one location for each of the plurality of gas stations. The computer is programmed to determine a first gas station of the plurality of gas stations based on the current location of the vehicle, the plurality of gas prices, and the plurality of locations such that driving the vehicle from the current location to the first gas station and then to a final destination requires a first cost of gas, which is less than or equal to the cost of gas of driving the vehicle from the current location to any other gas station and then to the final destination. The data concerning the current location of the vehicle may be received from a global positioning system.